Phosphorylation of skeletal muscle calsequestrin enhances its Ca2+ binding capacity and promotes its association with junctin

Nicole BEARD, Lan Wei, Stephanie Cheung, Takashi Kimura, Magdolna Varsanyi, Angela F. Dulhunty

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Calcium signaling, intrinsic to skeletal and cardiac muscle function, is critically dependent on the amount of calcium stored within the sarcoplasmic reticulum. Calsequestrin, the main calcium buffer in the sarcoplasmic reticulum, provides a pool of calcium for release through the ryanodine receptor and acts as a luminal calcium sensor for the channel via its interactions with triadin and junctin. We examined the influence of phosphorylation of calsequestrin on its ability to store calcium, to polymerise and to regulate ryanodine receptors by binding to triadin and junctin. Our hypothesis was that these parameters might be altered by phosphorylation of threonine 353, which is located near the calcium and triadin/junctin binding sites. Although phosphorylation increased the calcium binding capacity of calsequestrin nearly 2-fold, it did not alter calsequestrin polymerisation, its binding to triadin or junctin or inhibition of ryanodine receptor activity at 1 mM luminal calcium. Phosphorylation was required for calsequestrin binding to junctin when calcium concentration was low (100 nM), and ryanodine receptors were activated by dephosphorylated calsequestrin when it bound to triadin alone. These novel data shows that phosphorylated calsequestrin is required for high capacity calcium buffering and suggest that ryanodine receptor inhibition by calsequestrin is mediated by junctin.
Original languageEnglish
Pages (from-to)363-373
Number of pages11
JournalCell Calcium
Volume44
Issue number4
DOIs
Publication statusPublished - 14 Mar 2008
Externally publishedYes

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Calsequestrin
Skeletal Muscle
Phosphorylation
Ryanodine Receptor Calcium Release Channel
Calcium
Sarcoplasmic Reticulum
Calcium Signaling
Threonine
Calcium Channels
Polymerization
Myocardium
Buffers
Binding Sites
triadin

Cite this

BEARD, Nicole ; Wei, Lan ; Cheung, Stephanie ; Kimura, Takashi ; Varsanyi, Magdolna ; Dulhunty, Angela F. / Phosphorylation of skeletal muscle calsequestrin enhances its Ca2+ binding capacity and promotes its association with junctin. In: Cell Calcium. 2008 ; Vol. 44, No. 4. pp. 363-373.
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Phosphorylation of skeletal muscle calsequestrin enhances its Ca2+ binding capacity and promotes its association with junctin. / BEARD, Nicole; Wei, Lan; Cheung, Stephanie; Kimura, Takashi; Varsanyi, Magdolna; Dulhunty, Angela F.

In: Cell Calcium, Vol. 44, No. 4, 14.03.2008, p. 363-373.

Research output: Contribution to journalArticle

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AU - Wei, Lan

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AU - Dulhunty, Angela F.

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AB - Calcium signaling, intrinsic to skeletal and cardiac muscle function, is critically dependent on the amount of calcium stored within the sarcoplasmic reticulum. Calsequestrin, the main calcium buffer in the sarcoplasmic reticulum, provides a pool of calcium for release through the ryanodine receptor and acts as a luminal calcium sensor for the channel via its interactions with triadin and junctin. We examined the influence of phosphorylation of calsequestrin on its ability to store calcium, to polymerise and to regulate ryanodine receptors by binding to triadin and junctin. Our hypothesis was that these parameters might be altered by phosphorylation of threonine 353, which is located near the calcium and triadin/junctin binding sites. Although phosphorylation increased the calcium binding capacity of calsequestrin nearly 2-fold, it did not alter calsequestrin polymerisation, its binding to triadin or junctin or inhibition of ryanodine receptor activity at 1 mM luminal calcium. Phosphorylation was required for calsequestrin binding to junctin when calcium concentration was low (100 nM), and ryanodine receptors were activated by dephosphorylated calsequestrin when it bound to triadin alone. These novel data shows that phosphorylated calsequestrin is required for high capacity calcium buffering and suggest that ryanodine receptor inhibition by calsequestrin is mediated by junctin.

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